Electrical cable thieves paralysed the train service in parts of western Germany overnight around the city of Bochum, with some delays expected to last into Friday afternoon.
Train traffic through Bochum and the surrounding Ruhr region was disrupted until midday on Friday, when repairs were completed on the signals and communications lines, a spokesman for German national rail operator Deutsche Bahn said.
Shorter disruptions also hit neighbouring areas of western Germany as well, according to Deutsche Bahn.
Bochum, located between the larger cities of Essen and Dortmund, sits in the heart of the Ruhr region, one of Europe's most densely populated areas.
Police caught and arrested two suspected thieves while they were stealing railroad cables near Bochum's central train station overnight, police said.
The attempted theft caused signal problems that forced the major disruptions to rail traffic.
The two men, aged 53 and 50, made extensive statements during interrogation, a federal police spokeswoman said on Friday. Police believe the thieves were after the metal in the cables, and there is no evidence of a deliberate attempt to sabotage rail operations.
A third perpetrator is still being sought. The suspects had cut about 25 metres of cable near the station overnight. That caused a failure message at the railroad, and police quickly arrived.
Long-distance trains were widely diverted. There were also cancellations and diversions on regional services and suburban trains.
Due to the cable theft, the Bochum signal box is no longer operational. In addition, radio traffic in the north of the state of North Rhine Westphalia was disrupted by the crime during the night, said the railway spokeswoman.
Train drivers were unable to reach the signal boxes and were therefore not allowed to continue their journeys for safety reasons.
According to the railway, freight trains and around 20 passenger lines were affected, but the railway was unable to immediately say how many trains were impacted.